Propulsion means for a boat

ABSTRACT

A propulsion aggregate for boats of planing type is disclosed. The aggregate ( 10 ) comprises at least one inboard engine ( 5 ) disposed in a supporting frame ( 6 ), at least one first drive shaft ( 1 ) having a propeller ( 3 ), which shaft ( 1 ) extends through the boat hull ( 11 ) at the stern section of the boat, at least one rudder ( 12 ), and a second drive shaft ( 2 ) that extends through the stern section of the boat and drives a water turbine ( 4 ). The first drive shaft ( 1 ) is in direct connection with the power take-off ( 7 ) of the engine ( 5 ) via a releasable coupling ( 8 ) and said first drive shaft ( 1 ) is in operation during forward propulsion above a certain speed only, and the second drive shaft ( 2 ) is connected to the power take-off ( 7 ′) of the engine ( 5 ) and is arranged at a higher level than the propeller ( 3 ) and said second drive shaft ( 2 ) is in operation at forward propulsion at low speeds and at reverse motion.

This application is the U.S. national phase of international applicationPCT/NO01/0033 filed 31 Jan. 2001, which designated the U.S.

The present invention relates to a propulsion aggregate for a boat ofplaning type, which aggregate comprises at least one inboard enginedisposed in a supporting frame, at least one first drive shaft having apropeller, which shaft extends through the boat hull at the sternsection of the boat and at least one rudder.

The propulsion aggregate is in particular developed with regard toplaning boats of smaller and medium sized type. The aggregate is inparticular suited for boat hulls which during high speeds just touch thewater surface at the stern section of the hull. This however, is not tobe understood as a limitation.

One object of the invention has been to provide a propulsion aggregatethat consists of as few components as possible and is to render internalfriction in the drive gear to a minimum.

In stern mounted aggregates having powerful engines, it has been aproblem to make the drive gear, which transmits the engine power to thepropeller, to last. It is not unusual that the drive gear has to beoverhauled once a year. It is further a known matter that the drive gearwithin the aggregate stern including transmission and its many gears, isa source to great losses in power output.

According to the present invention a propulsion aggregate of theintroductorily described type is provided, which is characterised inthat the aggregate comprises a second drive shaft that extends throughthe stern section of the boat and drives a water turbine, that the firstdrive shaft is in direct connection with the power take-off of theengine via a releasable coupling and is in operation during forwardpropulsion above a certain speed only, and that also the second driveshaft is connected to the power take-off of the engine and is arrangedat a higher level than the propeller and is in operation at forwardpropulsion at low speeds and at reverse motion of the boat.

The propeller can be a conventional boat propeller, optionally a surfaceacting propeller of the type that is designed for speedboats.

In a first embodiment the power take-off of the engine for the firstdrive shaft is directed forward of the boat, and this first drive shaftis extended to the power take-off and is connected to this via a powertransmission unit, and the power take-off for the second drive shaft isdirected rearwards. In practise this implies that a conventional inboardengine will be turned around having the engine front facing rearwardsand the flange of the crankshaft facing forwards.

In a second embodiment the power take-off of the engine for the firstand the second drive shafts are directed rearward of the boat and thefirst drive shaft is connected to the power take-off via a powertransmission unit. In practise this implies an engine that is arrangedwith the front thereof in normal speed direction.

Suitably the power transmission unit can be in form of a cogged belt andtwo supported pulleys that the cogged belt runs over.

It may be desired to have two propellers that are driven by one engine.In such an embodiment a third drive shaft corresponding to the firstdrive shaft can be arranged adjacent to and spaced apart from the firstdrive shaft, but at the same level, and the power transmission unit beso arranged that the shafts rotate in opposite directions.

In order to obtain substantial propulsion power, two engines can beinstalled. The propulsion aggregate do then have two inboard enginesplaced adjacent to each other and can, in a first embodiment, be soarranged that they have respective drive shafts and propellers rotatingin opposite directions.

In another embodiment the propulsion aggregate including the two inboardengines placed adjacent to each other, be so arranged that they have acommon drive shaft and propeller.

In a preferable embodiment the propulsion aggregate is tiltable about asubstantially horizontal axis that is located near the stern section ofthe boat. This provides an option to optimise the inclination of thestern drive shaft during driving in order to obtain best possible effectand speed of the boat.

One way to provide this is that the propulsion aggregate is tiltableabout the substantially horizontal axis by means of at least one workingcylinder that is located near the front end of the support frame.

Other and further objects, features and advantages will appear from thefollowing description of preferred embodiments of the invention, whichis given for the purpose of description, without thereby being limiting,and given in context with the appended drawings where:

FIG. 1 shows schematically a side view of a first embodiment of apropulsion aggregate according to the invention, mounted in the sternsection of a boat hull,

FIG. 2 shows schematically a side view of a second embodiment of apropulsion aggregate according to the invention, mounted in the sternsection of a boat hull,

FIGS. 3A-3D shows schematically the water line during four differentoperating conditions of a boat having the propulsion aggregate accordingto the invention,

FIGS. 4A-4D shows schematically some alternative combinations of thepropulsion engines and drive shafts in a propulsion aggregate accordingto the invention.

Reference is firstly given to FIG. 1 that shows a first embodiment of apropulsion aggregate 10 according to the invention. The propulsionaggregate 10 is located in the stern section of a boat hull 11. Thepropulsion aggregate 10 comprises a drive engine 5, which in thisembodiment is turned opposite the speed direction; i.e. the front of theengine 5 faces the stern of the boat. The Engine 5 is mounted to asupport frame 6 that is pivotably supported to a mount 15 at the sternsection of the boat. A working cylinder 16 is arranged between thebottom of the boat and the support frame 6 near the front end thereof.

A first drive shaft 1 is in driving connection with the engine powertake-off 7, i.e. the engine crankshaft, via a power transmission unit 9and a coupling such like a clutch 8. The power transmission unit 9consists briefly of an upper and lower pulley 14,14′, which areinterconnected by a cogged belt 13. The pulleys 14,14′ are supported inrespective bearings. The drive shaft 1 is at its font end supported inthe same bearing as the lower pulley 14′ and the drive shaft 1 isdirectly coupled to the lower pulley 14′. The first drive shaft 1 isalso supported in a second bearing near the boat stern. The drive shaft1 extends further rearwards through the boat stern and is sealed off bya lead-in boot 17 that prevents water penetration. The drive shaft 1 issupported at the rear end by a third bearing, and a propeller 3 is fixedto the rear end of the drive shaft 1. Preferably the bearings are of thesealed type and packed with grease. At each side of the propeller 3 isrespective rudders 12 arranged. Only one rudder 12 is shown.

A second drive shaft 2 is also mounted to the power take-off 7′ of theengine 5, i.e. the crankshaft, though in the front end of the engine 5,and the second drive shaft 2 is located at a higher level than the firstdrive shaft 1. The second drive shaft 2 is in direct connection with awater turbine 4 and these components are placed within an enclosingshell 18. The drive shaft 2 is supported to the shell 18 in a front andrear bearing. The shell 18 extends through the stern section of the boatand is external sealed off by a second boot 19. The shell 18 has anopening 20 facing downwards and operates as water suction. The shell 18also has a turbine opening 24 facing rearwards. Further, a baffle 21 isprovided that can be folded down when reversing the boat is needed. Therudders 12 extend all the way up to the sides of the turbine opening 24.

A brace 22 is secured to the shell 18 and extends down to the firstdrive shaft 1 and retains the rear bearing thereof. From the shell 18and the brace 22 are respective projecting arms 23,23′ provided, whichsupport the rudders 12. The rudders 12 are pivotally fixed to the arms23, 23′.

The operation and manoeuvring of the propulsion aggregate 10 will now bedescribed. At normal propulsion of the boat, i.e. from approximately 4knots and higher, the propeller 3 is used. As it appears, there does notexist any gearbox with those power losses that might cause. The driveshaft 1 for the propeller 3 is in direct connection with the crankshaftof the engine 5, though it can be engaged and disengaged by means of theclutch 8. If a certain gear ratio between the RPM of the engine and therevolution of the drive shaft is desired, this can be provided by havingdiffering diameter of the upper and lower pulleys 14, 14′. This,however, is relations which should be matched for each individual boatin respect of the parameters; power output, type of propeller, hulldesign and size of the boat. This, however, will not be closer detailedhere.

During slow propulsion of the boat, e.g. when the boat is to ease offtowards a pier, or during troll fishery, the water turbine 4 is used.The water turbine 4 collects the water from the suction 20, draws thewater through the turbine 4 and ejects the water out through the turbineopening 24 at the rear end of the shell 18. During reverse operation,the reverse baffle 21 is turned and guided down in front of the turbineopening 24 and thus redirects forwardly the water flow ejected from theopening 24. A more detailed description of the four operating conditionswill be given later with reference to FIGS. 3A-3D.

A second embodiment of the propulsion aggregate 10′ will now bedescribed with reference to FIG. 2. Those components corresponding withthose in FIG. 1 are given the same reference numbers and will not bedescribed in detail once more. The engine 5 is like before placed in asupporting frame 6 that is pivotable about a horizontal axis through themount 15.

The major difference between the two embodiments is that the engine 5now is placed in the “correct” direction having the front thereof facingin the speed direction of the boat, and the power transmission unit 9 isplaced in the rear end near the stern of the boat. A coupling, or aclutch, is also present. It is not depicted, but can either be placedelevated adjacent to the first pulley 14 or lower adjacent to the secondpulley 14′. The second drive shaft 2 is, like before, in directconnection with the crankshaft of the engine 5. The first drive shaft 1is substantially shortened in respect of the one shown in FIG. 1 and hastwo bearings or supports only.

The shell 18 is slightly modified for adaption to the power transmissionunit 9, but is otherwise entirely corresponding to the one shown in FIG.1. For illustrating purposes, the rudder 12 is slightly differentdesigned and placed in the FIG. 2 embodiment. The turbine opening 24will in this embodiment be in form of a turnable nozzle, which is usedto manoeuvre the boat at low speeds and reversing (together with thebaffle 21). The rudder 12, which now is one single one, is used athigher speeds.

The advantage with this embodiment is that a more compact unit having asubstantially shorter first drive shaft 1 than the first embodiment isprovided. An advantage with the first embodiment will be the possibilityfor a lower construction height, i.e. lowest possible centre of gravityin the placing of the engine near the bottom of the boat.

Reference is now given to FIGS. 3A-3D showing four different operatingconditions. FIG. 3A shows slow speed, e.g. 0-4 knots, by use of thewater turbine and the propeller drive disengaged. The shell 18 includingthe suction 20 is fully submerged in the water, cf. the water line W.This figure will also be typical for reversing, except that the baffleplate 21 will be turned down in front of the turbine opening 24.

FIG. 3B shows semi planing speed of the boat and how the water line Wthen is positioned. The speed will typically be in the range of 4-15knots. The propeller 3 is engaged, but has relatively low rotationalspeed. At a certain speed the water turbine 4 will drop out in that thesuction 20 is lifted out of the water.

FIG. 3C shows planing speed and how the water line W then is positioned.Typical speed will be 15-25 knots. The propeller 3 has higher rotationalspeed and the water turbine 4 including the suction 20 is completely outof the water. The water turbine 4 will continue to rotate, since it isdirectly coupled to the power take-off, but has no function.

FIG. 3D shows super speed and how the water line W then is positioned.Typical speed will be over 25 knots. The propeller 3 has high rotationalspeed and the water turbine 4 is rotating, but the turbine is not inaction. In order to obtain this state, a surface acting propeller isnormally needed.

It is to be understood that the propulsion aggregate can be combined inmany ways in regard of number of engines, the placement of the engines,type of engines such as straight and V-engines, number of propellershafts and the sense of rotation thereof. FIGS. 4A-D illustrate some ofthe possibilities of combination. FIG. 4A shows one engine and onepropeller shaft. The arrow shows the sense of rotation. FIG. 4B showsone engine and two propeller shafts and related senses of rotation. Notethat a gear or the like is needed to alter the sense of rotation of oneof the shafts. Always when it is two propellers in question, they shouldrotate in opposite sense in order to obviate that the boat is pulledaside.

FIG. 4C shows two engines and one drive shaft. One variant of thepropulsion aggregate shown in FIG. 4C, is two engines driving oneanother propeller shaft in which the one shaft is lying centrally withinthe other, a duo prop aggregate. In duo prop aggregates, the propellerswill rotate in opposite directions. FIG. 4D shows two engines and twodrive shafts. The arrows show senses of rotation. It is further possibleto arrange two (or more) engines after each other and operate one or twoshafts as otherwise illustrated in FIGS. 4A-4D.

1. A propulsion aggregate for boats of planing type, which aggregatecomprises at least one inboard engine disposed in a supporting frame, atleast one first drive shaft having a propeller, which shaft extendsthrough the boat hull at the stem section of the boat, and at least onerudder, wherein the aggregate comprises a second drive shaft thatextends through the stem section of the boat and drives a water,turbine, the first drive shaft is operatively coupled to a powertake-off of the engine via a releasable coupling and said first driveshaft is in operation during forward propulsion above a certain speedonly, and the second drive shaft is connected to a power take-off of theengine and is arranged at a higher level than the propeller and saidsecond drive shaft is in operation at forward propulsion at low speedsand at reverse motion of the boat.
 2. A propulsion aggregate accordingto claim 1, characterised in that the propeller is a conventional boatpropeller.
 3. A propulsion aggregate according to claim 1, characterisedin that the power take-off of the engine for the first drive shaft isdirected forward of the boat, that the first drive shaft is extended tothe power take-off and is connected to this via a power transmissionunit, and the power take-off for the second drive shaft is directedrearwards.
 4. A propulsion aggregate according to claim 1, characterisedin that the power take-off of the at least one engine is common for thefirst and the second drive shafts and are directed rearward of the boatand the first drive shaft is connected to the power take-off via a powertransmission unit.
 5. A propulsion aggregate according to claim 3,characterised in that the power transmission unit is in form of a coggedbelt and two supported pulleys that the cogged belt runs over.
 6. Apropulsion aggregate according to claim 1, characterised in that a thirddrive shaft corresponding to the first drive shaft, is arranged adjacentto and spaced apart from the first drive shaft, but at same level, andthe power transmission unit is so arranged that the shafts rotate inopposite directions.
 7. A propulsion aggregate according to claim 1,characterised in that the aggregate has two inboard engines placedadjacent to each other and is so arranged that they have respectivedrive shaft and propeller rotating in opposite directions.
 8. Apropulsion aggregate according to claim 1, characterised in that theaggregate has two inboard engines placed adjacent to each other and isso arranged that they have common drive shaft and propeller.
 9. Apropulsion aggregate according to claim 1, characterised in that thepropulsion aggregate is tiltable about a substantially horizontal axisthat is located near the stern section of the boat.
 10. A propulsionaggregate according to claim 9, characterised in that the propulsionaggregate is tiltable about said substantially horizontal shaft by meansof at least one working cylinder located near the front end of thesupport frame.
 11. A propulsion aggregate according to claim 1,characterized in that the propeller is a surface acting propeller of thetype designed for speed boats.